The inventive concept relates to nonvolatile semiconductor memory devices. More particularly, the inventive concept relates to 3-dimensional nonvolatile semiconductor memory devices.
Semiconductor memory devices may be classified as volatile and nonvolatile devices.
Volatile memory devices lose their stored data when the power being supplied to the devices is turned off. Examples of volatile memory devices include static RAMs (SRAMs), dynamic RAMs (DRAMs), and synchronous DRAM (SDRAMs). Nonvolatile memory devices, on the other hand, retain their stored data even when the power being supplied thereto is cut off. Therefore, nonvolatile memory devices are widely used in portable electronics, such as mobile phones and MP3 players. Examples of nonvolatile memory devices include read only memories (ROMs), programmable ROM (PROMs), electrically programmable ROMs (EPROMs), electrically erasable and programmable ROM (EEPROMs), flash memory devices, phase-change RAMs (PRAMs), magnetic RAMs (MRAMs), resistive RAMs (RRAMs), and ferroelectric RAMs (FRAMs). Flash memory devices can be roughly divided into NOR type and NAND type of devices.
Because of the growing demand for smaller portable electronics that can store greater amounts of data and perform greater numbers of functions, there is a corresponding demand for more highly integrated semiconductor devices, especially nonvolatile memory devices. To this end, semiconductor memory devices having a three-dimensional array of memory cells are being developed to provide increased integration density and data storage capacity.